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Updated: Jun 28, 2026

Sampling and Pretreatment of Tooth Enamel Carbonate for Stable Carbon and Oxygen Isotope Analysis
Published on: August 15, 2018
Separate evolutionary origins of teeth from evidence in fossil jawed vertebrates
Moya Meredith Smith1, Zerina Johanson
1Craniofacial Development, Dental Institute, King's College London, Guy's Campus, London Bridge, London SE1 9RT, UK. moya.smith@kcl.ac.uk
Abstract:
Placoderms are extinct jawed fishes of the class Placodermi and are basal among jawed vertebrates. It is generally thought that teeth are absent in placoderms and that the phylogenetic origin of teeth occurred after the evolution of jaws. However, we now report the presence of tooth rows in more derived placoderms, the arthrodires. New teeth are composed of gnathostome-type dentine and develop at specific locations. Hence, it appears that these placoderm teeth develop and are regulated as in other jawed vertebrates. Because tooth development occurs only in derived forms of placoderms, we suggest that teeth evolved at least twice, through a mechanism of convergent evolution.
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